Silencing of the DNA Mismatch Repair Gene MLH1 Induced by Hypoxic Stress in a Pathway Dependent on the Histone Demethylase LSD1

• DOI: 10.1016/j.celrep.2014.06.035
• Publication Date: 2014-07-17T11:46:20Z
• Authors: Yuhong Lu; Narendra Wajapeyee; Mitchell S. Turker; Peter M. Glazer
• Keywords: Histone Demethylases; 0303 health sciences; QH301-705.5; Nuclear Proteins; Nerve Tissue Proteins; Decitabine; Cell Hypoxia; 3. Good health; 03 medical and health sciences; Colonic Neoplasms; Azacitidine; MCF-7 Cells; Humans; Gene Silencing; Biology (General); MutL Protein Homolog 1; Co-Repressor Proteins; DNA Modification Methylases; Adaptor Proteins, Signal Transducing; HeLa Cells

Silencing of MLH1 is frequently seen in sporadic colorectal cancers. We show here that hypoxia causes decreased histone H3 lysine 4 (H3K4) methylation at the MLH1 promoter via the action of the H3K4 demethylases LSD1 and PLU-1 and promotes durable long-term silencing in a pathway that requires LSD1. Knockdown of LSD1 or its corepressor, CoREST, also prevents the resilencing (and associated cytosine DNA methylation) of the endogenous MLH1 promoter in RKO colon cancer cells following transient reactivation by treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-dC). The results demonstrate that hypoxia is a driving force for silencing of MLH1 and that the LSD1/CoREST complex is necessary for this process. The results reveal a mechanism by which hypoxia promotes cancer cell evolution to drive malignant progression through epigenetic modulation. Our findings suggest that LSD1/CoREST acts as a colon cancer oncogene by epigenetically silencing MLH1 and also identify the LSD1/CoREST complex as a potential target for therapy.